Safety and arming device

ABSTRACT

1. A safety and arming device for underwater ordnance items comprising A HOUSING, A DETONATOR MOUNTED ON SAID HOUSING. A BOOSTER MOUNTED ON SAID HOUSING IN AXIAL ALIGNMENT WITH SAID DETONATOR, A SHUTTER MOVABLY MOUNTED ON SAID HOUSING BETWEEN SAID DETONATOR AND SAID BOOSTER, A TRANSMISSION CHARGE CARRIED BY SAID SHUTTER AND OPERABLE TO COMPLETE AN EXPLOSIVE TRAIN WHEN AXIALLY ALIGNED WITH SAID DETONATOR AND SAID BOOSTER. RESILIENT MEANS NORMALLY URGING SAID SHUTTER AND SAID TRANSMISSION CHARGE OUT OF AXIAL ALIGNMENT WITH SAID DETONATOR AND SAID BOOSTER WHEREBY THE EXPLOSIVE TRAIN IS INTERRUPTED AND THE ORDNANCE ITEM IS DISARMED, AND A FLOAT HAVING A SPECIFIC GRAVITY LESS THAN ONE POSITIONED WITHIN A CAVITY IN SAID HOUSING IN FLUID COMMUNICATION WITH THE WATER WHEN THE HOUSING IS IMMERSED THEREIN AND DIRECTLY CONNECTED TO SAID SHUTTER WHEREBY, UPON IMMERSION OF THE ORDANCE ITEM IN WATER, SAID SHUTTER IS MOVED BY SAID FLOAT AGAINST THE URGING OF SAID RESIIENT MEANS TO AXIALLY ALIGN SAID TRANSMISSION CHARGE WITH SAID DETONATOR AND SAID BOOSTER TO COMPLETE THE EXPLOSIVE TRAIN AND ARM THE ORDNANCE ITEM.

United States Patent [191 Fisher Dec. 10, 1974 SAFETY AND ARMING DEVICE[7S] lnventor: Lyman C. Fisher, Silver Spring, Md.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

[22] Filed: Dec. 30, 1963 [21) Appl. No.: 334,668

[52] US. Cl. 102/16 [51] Int. Cl. F42b 22/26 [58] Field of Search 102/7,10, 13, 16

[56] References Cited UNITED STATES PATENTS 1,473,148 11/1923 Hammond,Jr. 102/7 2,960,030 11/1960 Semon 102/16 Primary Examiner--Verlin R.Pendegrass Attorney, Agent, or Firm-Q. B. Warner [57] ABSTRACT I. Asafety and arming device for underwater ordnance items comprising ahousing,

a detonator mounted on said housing.

a booster mounted on said housing in axial alignment with saiddetonator,

a shutter movably mounted on said housing between said detonator andsaid booster,

a transmission charge carried by said shutter and operable to completean explosive train when axially aligned with said detonator and saidbooster.

resilient means normally urging said shutter and said transmissioncharge out of axial alignment with said detonator and said boosterwhereby the explosive train is interrupted and the ordnance item isdisarmed, and

a float having a specific gravity less than one positioned within acavity in said housing in fluid communication with the water when thehousing is immersed therein and directly connected to said shutterwhereby, upon immersion of the ordance item in water, said shutter ismoved by said float against the urging of said resiient means to axiallyalign said transmission charge with said detonator and said booster tocomplete the explosive train and arm the ordnance item.

l0 Claims, 5 Drawing Figures PATENIEU BE: 1 0 m4 NEH IN 2 FIG. I yman C.Fisher INVENTOR. JAMQ 4/1),

ATTORNEY PATENTED 3.853.056

SHEH 2 OF 2 FIG. 3

E FIG. 4 :l L FIG. 5 11"46 Lyman C. Fisher INVENTOR.

aid 0 mm) ATTORNEY SAFETY AND ARMING DEVICE The invention describedherein may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

This invention relates to safety and arming devices for underwaterordnance items, and more particularly to safety and arming devices forshallow water mines which operate independently of the ambienthydrostatic pressure.

ln the past, safety and arming devices for mines have normally usedhydrostatic pressure to provide environmental safety, i.e., the mine hadto be in the water and deep enough for hydrostatic pressure to move anexplosive train into alignment or operate electrical safing and armingswitches. In these prior art devices, hydrostatic pressure is normallyopposed by a spring and whatever ambient pressure exists inside thesealed mine case. This internal pressure varies, depending on theatmospheric conditions of temperature and pressure existing when thecase was sealed, relative to the condition of the air in the mine caseat the time arming occurred. This variation is large enough so thatproduction devices which will not arm in air, an unsafe condition, havebeen found to require submergence in as much as R8 to feet of water toinsure arming. Designers have employed evacuated bellows in an endeavorto overcome this difficulty but again, in production, such devices havebeen found to require at least 12 feet submergence for reliableoperation despite great care in design and manufacture.

The disadvantages and shortcomings of the prior art devices are apparentfrom the above discussion. The prior art devices will not provide safetyand arming for tethered or free floating mines, or for moored or bottommines in depths less than l2 to l8 feet. Yet there are many rivers andcanals which could be mined which are not this deep. For these reasons.designers have long sought a device which would sense that a mine wasreally in water, not just wet by rain or spray to provide environmentalsafety in very shallow bottom mines and in tethered or free floatingmines.

It is therefore a primary object of the present invention to provide newand improved safety and arming devices for underwater ordnance itemswhich are independent of hydrostatic pressure.

It is another object of this invention to provide safety and armingdevices for underwater ordnance items which will sense the immersion ofthe ordnance items in water as distinguished from the wetting of theordnance items by spray or rain.

It is a further object of this invention to provide safety and armingdevices for underwater ordnance items, the operation of which isindependent of the orientation of the ordnance items.

It is yet another object of this invention to provide safety and armingdevices for underwater ordnance items incorporating features whichpreclude arming of the ordnance items in air.

It is a still further object of this invention to provide safety andarming devices for underwater ordnance items which are readily adaptablefor use in bottom, tethered, and free floating mines.

With these and other objects in view, the present invention contemplatessafety and arming devices for underwater ordnance items which comprisean explosive detonator and an explosive booster charge mounted in axialalignment on a housing which may be attached to or formed in the casingof an underwater ordnance item. The detonator is intended for connectionto the firing mechanism of the ordnance item and the booster charge isadapted to trigger the main charge of the ordnance item. The detonatorand booster are spaced apart and a shutter carrying an explosivetransmission charge is interposed therebetween. The shutter provides theprincipal safety feature of the invention by precluding ignition of thebooster by operation of the detonator unless the shutter is sopositioned that the transmission charge carried by the shutter isaxially aligned with the detonator and booster to complete the explosivetrain. Resilient means are connected to the shutter and normally biasthe shutter to a safe position wherein the transmission charge is out ofaxial alignment with the detonator and booster. A float having aspecific gravity less than one is connected to the shutter and, uponimmersion of the ordnance item in water, moves the shutter in oppositionto the resilient means to an armed position wherein the transmissioncharge is axially aligned with the detonator and booster and theexplosive train is completed. An arming wire, which is withdrawn justbefore the ordnance item is laid, is connected to the shutter and holdsthe shutter in the unarmed position prior to withdrawal thereof topreclude inadvertent arming of the ordnance item in air. A solublewasher is also connected to the shutter for holding the shutter in asafe position until the washer dissolves after immersion of the ordnanceitem. This feature permits the laying vessel time to leave the immediatevicinity of the ordnance item before the item is fully armed.

Other objects, advantages and novel features of the present inventionwill become readily apparent upon consideration of the followingdetailed description when read in conjuction with the accompanyingdrawings wherein:

FIG. 1 is a sectional view illustrating one embodiment of the presentinvention; and

FIGS. 2-5 illustrate other embodiments of the present invention anddiffer from FIG. 1 principally in the specific arrangements utilized forconnecting the float to the shutter.

Attention now is directed to the drawings wherein like numerals ofreference designate like parts throughout the several views, and moreparticularly to FIG. 1 wherein one embodiment of the safety and armingdevice of the present invention is illustrated and is designatedgenerally by the reference numeral 10. The device 10 comprises a housing11 adapted to be secured to a casing 12 of a mine or other underwaterordnance item by means of screws 14. A closure member 15 is secured toone end of the housing H by screws 16 and forms a part of the housing.An explosive detonator l8 and an explosive booster charge 19 aredisposed in appropriately sized recesses in the member 15 in positionsof axial alignment. The detonator I8 is provided with leads 20 which areprovided for connecting the detonator to the firing mechanism (notshown) of the ordnance item. Booster charge 19 is adapted to initiatethe main charge (not shown) of the ordnance item upon detonationthereof.

A shutter 21 is slidably disposed within a recess 22 formed in themember 15 and carries a transmission charge 24 in an appropriate recesstherein. A second transmission charge 25 is positioned adjacent thebooster 19 and is utilized merely for convenience in sealing. The secondtransmission charge 25 may be eliminated by relocation of the booster 19adjacent the transmission charge 24 and the shutter 21. The detonator18, transmission charges 24 and 25, and the booster 19 togetherconstitute an explosive train which, when properly aligned, will serveto transmit a detonation initiated in the detonator 18 to the maincharge of the ordnance item when the firing mechanism is actuated. Theshutter 21 is so designed that, when the elements are positioned asshown in FIG. 1, the shutter forms a detonation barrier and a detonationwave will not be transmitted across the recess 22 and thus an accidentalexplosion of the ordnance item due to inadvertent firing of thedetonator 18 is precluded.

A cork float 26 is secured in any suitable manner to the shutter 21 andserves to provide a buoyant force for moving the shutter, in thedirection indicated by the arrow in FIG. 1, whenever the device isimmersed in water. A guide pin 28 is fixed to the shutter 21 and ridesin a slot 29 formedin one wall of the recess of 22 to maintain thetransmission charge 24 axially oriented with respect to the detonator.18 and second transmission charge 25. A compression spring 30 isinterposed between the bottom of the recess 22 and one end of theshutter 21 and normally urges the shutter to the safe position shown inFIG. 1. The spring constant of the spring 30 is selected so that thespring will readily support the weight of the shutter 21 and float 26 inair and yet yield readily under the buoyant force applied to the shutter21 by the float 26 when the device 10 is im-.

mersed water to permit movement of the shutter to align the elements ofthe explosive train.

A soluble washer 31 is disposed about one end of the shutter 21, and byengagement with a snap ring 32 carried by the shutter, precludes armingof the device 10 due to a buoyant force on the float 26 until the washer31 has dissolved. This built-in delay permits the laying vessel towithdraw from the vicinity of the ordnance item prior to arming thereofso that the laying vessel itself does not actuate the firing mechanismof the ordnance item. An additional safety feature is provided by way ofan arming wire 34 disposed in an aperture in the shutter 21 whichprecludes movement of the shutter to the armed position irrespective ofother conditions until the arming wire is withdrawn.

In the embodiment shown in FIG. 2, the float 26 is connected to theshutter 21 by means of a connecting rod 35 and pivoted link 36. Asisobvious from FIG. 2, movement of the float 26 in the directionindicated by the arrow will result in alignment of the elements of theexplosive train. The shutter 21 and float 26 are connected to the casing12 by means of expansible bellows 38 and 39, respectively. The bellows38 and 39 perform the function performed by the compression spring inthe embodiment of FIG. land additionally, these bellows. beingoppositely acting, serve to offset the effects of hydrostatic pressure.In this embodiment, the shutter 21 extends through the opposite side ofthe casing 12 and is provided with a soluble washer 31, snap ring 32 andarming wire 34. These elements are not repeated in FIG. 2, for thepurpose of simplifying the drawing, since their construction isadequately illustrated in FIG. I.

In the embodiment of the FIG. 3, the shutter 21 extends all of the waythrough the mine casing 12 to compensate for the effects of hydrostaticpressure and is directly connected to the float 26, movement of which inthe direction of the arrow will align the explosive train. Flexiblediaphragms 40 of rubber or other suitable material are connected toopposite ends of the shutter 21 to provide a fluid seal. Again the endof the shutter 21 opposite the float 26 would be provided with thesoluble washer and arming wire in an arrangement similar to thatillustrated in FIG. 1.

In the embodiment of FIG. 4, the float 26 is illustrated as sphericaland is connected to" the shutter 21 by means of a flexible member 41.Brackets 42 are mounted on the casing 12 to support the float 26 in theposition shown in FIG. 4. As is evident from the drawing, movement offloat 26 in any of the three directions indicated by the arrows in thedrawing would result in movement of the shutter 21 to the armed positionwherein the explosive train elements are aligned. Again the other end ofthe shutter 21 is omitted for purposes of simplicity but would beprovided with a soluble washer and arming wire arrangement asillustrated in FIG. 1.

FIG. 5 illustrates an embodiment which is omnidirectional in function. Aspherical float 26 is mounted between a pair of L-shaped brackets 44which are pivotedly connected by means of a pivot pin 45 and which areprovided with open, circular loops 46 on the upper ends thereof. Theloops 46 are of a lesser diameter than the float 26 and serve to confinethe float therebetween. As before, the other end of the shutter 21 ispro vided with a soluble washer and arming wire arrangement similar tothat shown in FIG. 1.

OPERATION In order that a better understanding of the invention might behad, the mode of operation of the various disclosed embodiments will nowbe described. Immediately before laying the ordnance item, the armingwire 34 is extracted from the aperture in the shutter 21. The ordnanceitem is then laid in the water in any fashion appropriate to theparticular ordnance item. Immediately upon entry into the water, abuoyant force is applied to the float 26. However, immediate arming ofthe ordnance item is precluded by the action of the soluble washer 31engaging the snap ring 32. Upon dissolution of the soluble washer 31,the float 26 is free to move in response to the buoyant force thereon.As will be evident from the drawings, the embodiments of FIGS. 1, 2 and3 are limited to utilization in an ordnance item which will have a knownorientation with respect to the vertical. That is, the final orientationof the ordnance item must be such that the buoyant force on the float 26will be exerted in substantially the same direction as the arrows inthese FIGS. The buoyant force on the float 26 will then move theshutters 21 in the direction indicated by the arrows against the urgingof the compression spring 30, or in the case of FIG. 2 against theresistance of the bellows 38 and 39, to axially align the transmissioncharge 24 with the other elements of the explosive train to complete thetrain and thus arm the ordnance item. The main charge of the ordnanceitem will than be initiated at such time as the detonator 18 is tired bythe firing mechanism.

In the embodiment of FIG. 4, the orientation of the ordnance item is notas critical. As long as the buoyant force on the float 26 is not actingin a direction lying within the angle defined by the ends of thebrackets 42 and the center of the float 26, the float will roll out ofthe socket defined by the ends of the brackets and move the shutter 21against the urging of the compression spring 30 to align the elements ofthe explosive train. The member 41 is made flexible to accommodatemovement of the float 26 in any direction other than the verticaldirection as illustrated in FIG. 4.

On the other hand, the embodiment of FIG. 5 will function to arm theordnance item irrespective of the direction of the buoyant force on thefloat 26. If the buoyant force on the float 26 is in either of thevertical directions, the loops 46 will be forced apart by the flaotcausing the brackets 44 to pivot about their corners 48. This movementof the brackets 44 will cause the brackets to pivot about the pivot pin45 with respect to each other and thus elevate the pivot pin. Theshutter 21 is connected to the pivot pin 45 by means of the flexiblemember 41 and thus will be moved to the armed position by upwardmovement of the pivot pin. A flexible strap 49 interconnects thebrackets 44 and limits the spreading thereof to preclude escape of thefloat 26 from the confining action of the loops 46.

if the buoyant force on the float 26 is in one of the lateraldirections, the brackets 44 will move as a unit pivoting about one ofthe corners 48 and again raising the pivot pin 45 to extract the member41 which is flexible to accommodate this movement. A buoyant force onthis float 26 acting in a direction other than the mutuallyperpendicular directions shown in FIG. 5 will result in a movement ofthe brackets 44 which is a combination of the aforedescribed movementsbut which will still result in movement of the pin 45 away from thecasing 12 and alignment of the elements of the firing train.

Consideration of the aforedescribed embodiments by those skilled in theart will result in additional variants immediately suggestingthemselves. For example, internal operation of the device can also beaccomplished by providing a float action which will result in rotarymotion of the shaft, in which case hydrostatic forces are absent also.Additionally, internal motion can be effected through a lever pivoted ina ball or hinge type seal in the safety and arming device container walland mounting the float on the outer end thereof. Another possibilitywould be to incorporate the major portion of the positive buoyancy inthe float. In this case an ordnance item which sinks would do so becausethe float became flooded or ineffective and this would result indisarming or sterilizing of the ordnance item.

The linear motion of the float due to the buoyant force can also beapplied in various ways which are well known to designers of safety andarming mechanisms to provide environmental safety, i.e., to operateswitches, align explosive train shutters or rotors, or simply to removea gag from one of these devices so that they can be operated from othersources. For example, in a moored mine the float could be used simply tounlock the shutter when the mine enters the water. The shutter could bemoved to the armed position mechanically when the case separates fromthe anchor, or could be moved by an explosive driver initiated by asimple seawater cell uncovered when the case separates from the anchor,or initiated by an internal timer in the mine, started when the caseseparates from the anchor.

Also, it should be noted that while a cylindrical cork float was used asan example, there are many shapes and designs for floats equallysuitable for this use, in-

cluding hollow spherical or cylindrical or irregularly shaped metal andplastic floats, foamed plastic filled floats having metal, plastic orrubber sheaths, and floats made solely of foamed plastic. The solerequirement is that the float be of low specific gravity so that it willprovide the necessary positive buoyancy in water.

From the foregoing it will be readily apparent that the presentinvention provides numerous advantages not obtainable with prior artdevices. The present invention provides safety in air, rain, spray andhigh humidity, yet at the same time it provides a known force to arm orpermit arming of an ordnance item when just submerged in water or at anydepth. That is, in contrast to known methods, it senses immersion inwater with out dependence on submergence to some minimum depth foroperation.

it is to be understood that the aforedescribed embodiments are simplyillustrative of the principal features of the present invention.Numerous other arrangements may be readily devised by those skilled inthe art to achieve a similar device which will still embody theprinciples of the present invention and fall within the spirit and scopethereof.

What is claimed is:

l. A safety and arming device for underwater ordnance items comprising:

a housing,

a detonator mounted on said housing,

a booster mounted on said housing in axial alignment with saiddetonator,

a shutter movably mounted on said housing between said detonator andsaid booster,

a transmission charge carried by said shutter and operable to completean explosive train when axially aligned with said detonator and saidbooster,

resilient means normally urging said shutter and said transmissioncharge out of axial alignment with said detonator and said boosterwhereby the explosive train is interrupted and the ordnance item isdisarmed, and

a float having a specific gravity less than one positioned within acavity in said housing in fluid communication with the water when thehousing is immersed therein and directly connected to said shutterwhereby, upon immersion of the ordnance item in water, said shutter ismoved by said float against the urging of said resilient means toaxially align said transmission charge with said detonator and saidbooster to complete the explosive train and arm the ordnance item.

2. A safety and arming device as defined in claim 1 wherein a solubleelement is connected to said shutter for restraining said float fromarming the ordnance item until said soluble element has dissolvedwhereby the arming is delayed.

3. A safety and arming device as defined in claim 1 wherein a removablearming wire is connected to said shutter for restraining said float frommoving said shutter to the armed position prior to removal of said wirewhereby inadvertent arming of the ordnance item is precluded.

4. A safety and arming device as defined in claim I wherein said floatis formed of cork.

5. A safety and arming device as defined in claim 1 wherein said floatis a hollow metal float.

6. A safety and arming device as defined in claim 1 wherein said floatis formed of a foamed plastic material.

7. A safety and arming device for underwater ordnance items comprising:

a housing,

a detonator mounted on said housing,

a booster mounted on said housing in axial alignment with saiddetonator,

a shutter movably mounted on said housing between said detonator andsaid booster,

a transmission charge carried by said shutter and operable to completean explosive train when axially aligned with said detonator and saidbooster,

resilient means normally urging said shutter and said transmissioncharge out of the axial alignment with said detonator and said boosterwhereby the explosive train is interrupted and the ordnance item isdisarmed,

a float having a specific gravity less than one positioned within acavity in said housing in fluid communication with the water when thehousing is immersed therein and directly connected to said shutterwhereby, upon immersion of the ordnance item in water, said shutter ismoved by said float against the urging of said resilient means toaxially align said transmission charge with said detonator and saidbooster to complete the explosive train and arm the ordnance item,

a soluble washer connected to said shutter for restraining said floatfrom arming the ordnance item until said soluble washer has dissolvedwhereby the arming is delayed, and

a removable arming wire disposed in an aperture in said shutter forrestraining said float from moving said shutter to the armed positionprior to removal of said wire whereby inadvertent arming of the 0rdnance item is precluded.

8. A safety and arming device as defined in claim 7 wherein said floatis formed of solid cork.

9. A safety and arming device as defined in claim 7 wherein said floatis a hollow metal float.

10. A safety and arming device as defined in claim 7 wherein said floatis formed of a foamed plastic material.

1. A safety and arming device for underwater ordnance items comprising:a housing, a detonator mounted on said housing, a booster mounted onsaid housing in axial alignment with said detonator, a shutter movablymounted on said housing between said detonator and said booster, atransmission charge carried by said shutter and operable to complete anexplosive train when axially aligned with said detonator and saidbooster, resilient means normally urging said shutter and saidtransmission charge out of axial alignment with said detonator and saidbooster whereby the explosive train is interrupted and the ordnance itemis disarmed, and a float having a specific gravity less than onepositioned within a cavity in said housing in fluid communication withthe water when the housing is immersed therein and directly connected tosaid shutter whereby, upon immersion of the ordnance item in water, saidshutter is moved by said float against the urging of said resilientmeans to axially align said transmission charge with said detonator andsaid booster to complete the explosive train and arm the ordnance item.2. A safety and arming device as defined in claim 1 wherein a solubleelement is connected to said shutter for restraining said float fromarming the ordnance item until said soluble element has dissolvedwhereby the arming is delayed.
 3. A safety and arming device as definedin claim 1 wherein a removable arming wire is connected to said shutterfor restraining said float from moving said shutter to the armedposition prior to removal of said wire whereby inadvertent arming of theordnance item is precluded.
 4. A safety and arming device as defined inclaim 1 wherein said float is formed of cork.
 5. A safety and armingdevice as defined in claim 1 wherein said float is a hollow metal float.6. A safety and arming device as defined in claim 1 wherein said floatis formed of a foamed plastic material.
 7. A safety and arming devicefor underwater ordnance items comprising: a housing, a detonator mountedon said housing, a booster mounted on said housing in axial alignmentwith said detonator, a shutter movably mounted on said housing betweensaid detonator and said booster, a transmission charge carried by saidshutter and operable to complete an explosive train when axially alignedwith said detonator and said booster, resilient means normally urgingsaid shutter and said transmission charge out of the axial alignmentwith said detonator and said booster whereby the explosive train isinterrupted and the ordnance item is disarmed, a float having a specificgravity less than one positioned within a cavity in said housing influid communication with the water when the housing is immersed thereinand directly connected to said shutter whereby, upon immersion of theordnance item in water, said shutter is moved by said float against theurging of said resilient means to axially align said transmission chargewith said detonator and said booster to complete the explosive train andarm the ordnance item, a soluble washer connected to said shutter forrestraining said float from arming the ordnance item until said solublewasher has dissolved whereby the arming is delayed, and a removablearming wire disposed in an aperture in said shutter for restraining saidfloat from moving said shutter to the armed position prior to removal ofsaid wire whereby inadvertent arming of the ordnance item is precluded.8. A safety and arming device as defined in claim 7 wherein said floatis formed of solid cork.
 9. A safety and arming device as defined inclaim 7 wherein said float is a hollow metal float.
 10. A safety andarming device as defined in claim 7 wherein said float is formed of afoamed plastic material. >